Tissue engineering is an emerging field that aims to create biological substitutes for diseased or damaged tissues. A major challenge in the field of tissue engineering is creating two- and three-dimensional multi-cellular constructs with defined spatial organization of cells, to mimic the architecture of living tissues, where homotypic and heterotypic cellular interactions are key to tissue formation and function.
Current tissue engineering approaches focus on creating multi-cellular constructs from either the top-down or bottom-up. Both approaches seek to provide a supportive niche for cells to guide their proliferation, differentiation, and maturation and generate functional constructs. Although both classes show some promise, bottom-up approaches can potentially overcome limitations in cell placement and alignment that are difficult to achieve in most top-down approaches. Recently, a non-contact patterning method based on the use of aqueous two-phase systems has been adopted to autonomously dispense a suspension of cells without any actuation forces. See e.g. Tavana, H.; et al., Nanoliter liquid patterning in aqueous environments for spatially defined reagent delivery for mammalian cells. Nature Materials. 8, 736-41 (2009) and Tavana, H.; et al., Polymeric aqueous biphasic systems for non-contact cell printing on cells: engineering heterocellular embryonic stem cell niches. Adv Mater 2010, 22 (24), 2628-31, the disclosures of which are hereby incorporated by reference in their entirety. Unfortunately, these systems showed only the capability to print bioreagents and cells in arbitrary shapes, because printing was performed with manual liquid handling tools, it could only control droplet-shaped patterns.
What is needed in the art is an automated mechanism and related method for making three-dimensional tissue constructs with spatial organization of cells that provides: (i) organized cell placement and spatial assembly of multiple cell types in a reproducible manner (ii) direct and non-contact assembly of multiple cell types and/or cell layers without exerting damaging forces on the cells or tissues, (iii) retention of cell viability and functionality during assembly steps and long periods of culture, (iv) minimal use of harmful and toxic chemicals such as profuse amounts of mineral oil and buffer reagent, and (v) efficient layer-to-layer assembly of cell layers within the three-dimensional construct while (vi) avoiding the use of complicated surface treatments that prevents scale-up, and (vii) avoiding mutation-inducing radiations such as UV used to photocrosslink hydrogels.